1. Field of the Invention
The present invention relates to an assembly for providing an electrical connection between a high power transistor module and other electrical devices and more specifically relates to a bus bar assembly comprising a high power transistor module mounted to a multilayer laminated bus bar and to the method of connecting the two components.
2. Brief Description of the Related Art
Power distribution in modern electronic systems requires great care and consideration in configuring the distribution of several voltages and ground in electronic equipment. For example, a circuit board package in certain electronic equipment, such as middle- or large-scale computers, for instance, requires a supply of a large current of a predetermined voltage. It is common in many high-power applications for a high power transistor module, e.g., an integrated gate bipolar transistor (IGBT), to be provided. The IGBT modules are used featuring power electronic systems with high power density, high efficiency and good dynamic characteristics.
In mounting the IGBT modules to a power distribution system, the IGBT modules were in the past mounted on printed circuit boards (PCB""s) by soldering the IGBT module on the PCB, In addition, it is known to package several IGBT""s in one module for mounting on the electric distribution system. However, as electronic applications have evolved, these applications require higher and higher currents which prevent the IGBT modules from being mounted directly to printed circuit boards. As higher currents are realized, more heat is also generated by the IGBT modules and this heat disadvantageously results in operational problems for the PCB and the IGBT modules mounted thereto. Consequently, as the high power transistor modules continually increase the amount of current which passes therethrough, it is desirable to provide a new method of attaching high power transistors (IGBT modules) to electric distribution systems, especially when these high currents are used in the electric distribution systems.
The present invention relates to a bus bar assembly comprising a high power transistor module mounted to a multi layer laminated bus bar. Preferably, the high power transistor module comprises a module including at least one IGBT module having soldering pins which are received within corresponding soldering islands formed in the multi layer laminated bus bar to provide an effective and solid electrical connection therebetween.
In one exemplary embodiment, the multi layer laminated bus bar comprises a plurality of conducting plates and a plurality of conductive lugs, each disposed in either a first conducting plane or a second conducting plane. The plurality of conducting plates are arranged so that each plate is electrically connected to a corresponding positive or negative terminal of an electrical component, such as a high power transistor module which is easily mounted to the bus bar assembly. The plurality of lugs are arranged so that each lug is electrically connected to a phase terminal of the electrical component. The conducting plates and lugs are held in place in each respective plane by an electrically insulating outer coating which intimately encloses all of the conducting plates and lugs with the exception that an integral lug portion of each conducting plate and one end of the lugs extend beyond a peripheral edge at one side of the coating to define prongs which are intended to electrically connect the bus bar to an electrical device and provide power to the high power transistor module mounted thereto. Each conducting plate and lug is formed of a conductive material, e.g., copper with tinplating on outer surfaces thereof.
The conducting plates and lugs lying in the same plane are prevented from contacting one another by disposing the plates and lugs so that they are entirely separated from one another. Conducting plates and lugs in opposing planes are prevented from contacting one another by placing an inner insulating material between the planes. Consequently, each conducting plate or lug is prevented from contacting another, thereby eliminating a short circuiting event between two conducting surfaces. It being understood that the above described bus bar is merely exemplary in nature and other suitable bus bars may be used in accordance with the present invention.
In the present invention, the bus bar is designed to be directly mounted to the high power transistor module to form the bus bar assembly. To accomplish this the bus bar has an improved solderability characteristic and is designed so that a solid, effective soldered connection results during a conventional soldering process in which the high power transistor module is securely mounted to the bus bar to form the bus bar assembly of the present invention. Accordingly, the soldering process involves soldering a pin which is a part of the high power transistor module to a surface of the bus bar using sufficient heat. The improved solderabilty of the present bus bar results by forming a soldering island in each conducting plate and lug at a predetermined point thereof. The soldering island comprises a central soldering opening, which receives the soldering pin, and a plurality of thermal barrier openings distributed around the soldering opening. The soldering island itself is generally defined as the area extending between the thermal barrier openings and each soldering island serves to accelerate the heating up of the soldering surface by limiting the amount of heat dissipation in the soldering surface. Accordingly, the likelihood of a cold solder connection is eliminated or substantially alleviated by limiting heat dissipation during the soldering process, and a secure mounting connection is formed between the two components which form the bus bar assembly of the present invention.
The present invention permits the current higher power transistor modules to be directly mounted to the bus bar resulting in improved internal management of the high power transistor module in comparison with a more conventional PCB. Because the bus bar has an improved current carrying capacity resulting in the bus bar not heating up as much as a conventional PCB, the high power transistor module is better suited for mounting with the bus bar to provide an improved assembly.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.